A majority of the directors shall be residents of the county or counties in which the district is located. Except as provided in section 31-409.03, any person or the officer or representative of any corporation owning or controlling any land assessed for benefits may be a director. The person elected a director receiving the least number of votes shall hold office for one year, the next higher for two years, and so on, and the term of each shall be adjusted so as to make the term of one director expire each year. The officers, consisting of a president, a treasurer, and a secretary, shall be chosen by the directors from their own number and for a term of one year. Unless the directors choose by February fifteenth of a given year to use the procedures provided in section 31-409.01, annual elections of directors shall be held on the second Tuesday of April each year, at the county courthouse or at such other place designated by the board pursuant to section 31-409.03. The annual election shall be omitted if such date occurs less than nine months after the first election. Vacancies in the office of directors may be filled by the remaining directors until the next election. All directors and officers shall hold office until their successors are elected and qualified.